Progut® Extra proven to reduce Salmonella pressure in broilers

Salmonella continues to be one of the major burdens of the broiler chicken industry. The global annual costs are measured in multiple billions of dollars. While some Salmonella strains are pathogenic to chickens, a large part of the economic impact comes from human healthcare costs.

Salmonella is a risk to humans and economic burden to poultry industry

Totally preventing the occurrence of Salmonella in layer and meat chickens is possible. However, it requires very strict procedures and close collaboration between all parties in the food chain. In Finland, a zero tolerance for Salmonella in the food chain has been maintained for decades. Most other countries focus on restricting its occurrence but allow a low prevalence of Salmonella in poultry.

Progut®Extra binds to Salmonella cells and prevent the colonization

Fimbriae enable Salmonella attachment to the intestinal surface

Most Salmonella strains have fimbriae which are thin, hair-like protein structures. The colonization of Salmonella in poultry begins when the bacterium attaches to the gut surface using its fimbriae. These fimbriae act as attachment organs. They recognize specific molecular structures on the intestinal surface of the host and bind to these target molecules. Once Salmonella attaches to the intestinal surface, it can penetrate the epithelium. From there, it may spread and colonize internal organs such as the liver. One key to successful Salmonella prevention is thus to inhibit the action of the fimbriae.

Mimicking gut surface molecules prevents bacterial attachment

The attachment of Salmonella can be prevented by blocking its fimbriae. This can be achieved using molecular mimetics that imitate the gut surface molecules the fimbriae would normally attach to. These molecular mimetics or “decoys”, can be produced by specific slicing of Saccharomyces yeast cell by acid hydrolysis.

Hydrolyzed yeast provides bioavailable binding site

Yeast cell wall consists of tightly interlinked layers of mannoproteins, beta-glucan and chitin. Intact yeast cells are not efficient at binding Salmonella. Their molecular structures are tightly linked and therefore not in a bioavailable form.

An optimized and well-studied acid hydrolysis of spent Saccharomyces yeast culture releases a rich variety of water-soluble binding sites. These sites can bind to the fimbriae of Salmonella and E. coli. This is the production process of Progut® Extra, the original postbiotic pathogen magnet. In addition to preventing the attachment of Salmonella and E. coli to the chicken gut, Progut® Extra helps strengthen the birds’ immune system.

Controlled Salmonella challenge trial with Progut® Extra

A controlled trial was run at Poulpharm, Belgium, to prove the efficacy of Progut® Extra in reducing Salmonella colonization and shedding in broiler chicken.

Experimental setup and housing conditions

The trial took place in poultry house of Poulpharm animal centre, in isolators measuring 1 m² and a height of 1 m. One commercial pan feeder with a feed reservoir was hung on the inside each isolator. Three  drinking nipples were also provided per isolator. The isolators were thoroughly cleaned and disinfected prior to the experiment.

Dietary treatments

The study included three dietary treatments,

1. Non-treated control diet
2. Control diet + Progut® Extra at 1 kg/ton
3. Control diet + Progut® Extra at 2 kg/ton

Chick management and monitoring

The chickens of Ross 308 breed arrived to the research farm as eggs, eight days pre-hatching. Once they had hatched, 60 chickens were allocated into the dietary treatment groups, 20 chickens/group. The clinical condition of the chickens was evaluated as described in ‘Broiler Signals, a practical guide by De Gussem et al.’, including clean and uninfected navel, active behaviour,  no malformations, absence of depression and no hunched posture. All chickens received an individually-numbered neck tag. No vaccination, antimicrobial or anti-inflammatory medication was administered to any of the chicks at any time point. Feed and water was freely available throughout the experiment. The chickens were tightly monitored on a daily basis for any changes in their condition.  

Salmonella challenge procedure

The Salmonella Enteritidis challenge inoculum was prepared at 2.55 x10⁸ CFU/ml from a fresh culture of the Poulpharm F.67.33 SE strain. The challenge was administered individually to every bird by oral gavage of 0.5 ml at 7 days of age.

Sampling and analysis

The efficacy of dietary treatments was assessed through sampling of cloacal swabs on days 3, 5, 7 and 14 days post-challenge. On day 7 post-challenge, 10 chicks/treatment were euthanized and sampled for liver tissue, which was then analysed for the presence of Salmonella. Between days 7 and 14, each treatment thus group consisted of 10 chickens. All remaining chickens were euthanized on day 14, and sampled and analysed for the presence of Salmonella in liver tissue.     

It is worth noting that in this experiment, the analysis only showed whether Salmonella was present or not in each sample type. The results did not include any quantification of Salmonella per sample.

Results

All chickens remained in normal condition throughout the study. No treatment- or challenge-related morbidity or mortality was observed.

Progut® Extra reduced Salmonella shedding in feces

Shedding of Salmonella via feces was assessed by analysis of cloacal swabs for the presence of Salmonella.  On day 3 post-challenge, at or over 80% of the chickens showed Salmonella-positive cloacal swabs, indicating active shedding of Salmonella to feces (Figure 1).

Lower proportion of Salmonella-positive swabs with Progut® Extra

In the control group, active Salmonella shedding continued on day 5 post-challenge. In contrast, a lower percentage of Salmonella-positive cloacal swabs was detected in the Progut® Extra–amended treatments. On day 5, the average reduction of Salmonella shedding by Progut® Extra was 27.5%, compared to the Control treatment (Figure 2).

On days 7 and 14 post-challenge, the Salmonella shedding activity was lower also in the Control treatment, compared to days 3 and 5. Dietary Progut® Extra was however able to induce a further decrease in the number of Salmonella-positive cloacal swabs (Figure 1). For both days 7 and 14, the mean reduction in the Salmonella shedding was 16.7% lower than that of the Control treatment (Figure 2).  

Significant reduction in liver colonization at higher Progut® Extra dose

The colonization of Salmonella into liver tissue on days 7 and 14 is presented in Figure 3. On day 7 post-challenge, 70-80% of all sampled chickens (10 chickens/group) showed Salmonella-positive livers. On day 14, all the ten Control chickens had Salmonella in liver tissue. Dietary Progut® Extra amendment at 1 kg/ton of feed reduced the liver Salmonella colonization by 10% (NS), while the 2 kg/ton dosing reduced the liver Salmonella colonization by 60% (p = 0.01).

Summary and Conclusions

In the present experiment, broiler chicken hatchlings were housed into three isolator units, initially 20 chickens per isolator. The birds were tagged for individual recognition. Each isolator represented one of the three dietary treatment groups: Non-treated control, Progut® Extra at 1 kg/ton and Progut® Extra at 2 kg/ton. Feed and water was available ad lib. throughout the experiment.

On day 7, the birds were orally challenged by Salmonella Enteritidis. The fecal shedding and liver colonization of Salmonella was followed from individual birds for 14 days by assessing the presence or absence of Salmonella in cloacal swabs on days 3, 5, 7 and 14, and in liver tissue on days 7 and 14.

Dietary Progut® Extra amendment demonstrated notable potential in Salmonella inhibition: the average efficacy of Progut® Extra treatments in reducing fecal Salmonella shedding was 16.7% – 27.7% on days 5-14 post-challenge. The 2g/kg dosing showed a higher efficiency in reducing fecal shedding of Salmonella than the 1 kg/ton dosing.

Colonization of livers by Salmonella was not affected by treatments on day 7 post-challenge. However, Progut® Extra at 2 kg/ton remarkably and statistically significantly reduced liver Salmonella colonization by 60%, compared to Control, while the efficacy of the 1 kg/ton dosing was 10%.

Key results with Progut® Extra:

• Reduced fecal Salmonella Enteritidis shedding by 16.7–27.7% on days 5–14 post-challenge
• At 2 kg/ton, decreased liver colonization by 60% (p = 0.01) compared to control
• No negative effects on bird health or behavior observed
• Demonstrates strong potential for reducing Salmonella pressure in broiler production

In conclusion, the present experiment suggests that dietary Progut® Extra amendment at sufficient level can be a highly effective strategy to reduce Salmonella pressure in commercial poultry production.

Supported by additional international findings

This conclusion is backed up by other experiments which have e.g. proven the superior ability of Progut® Extra to bind Salmonella cells in vitro and to reduce Salmonella counts in commercial broiler halls in the United States (-86% reduction in Salmonella counts in boot swabs between days 31 (pre-administration) and 45 (post-administration of 1.8 kg/ton of feed).  

Read more: